1202.3994 (A. T. Hanbicki et al.)

Electrical injection and detection of spin accumulation in Ge at room
temperature    [PDF]

A. T. Hanbicki, S. -. F. Cheng, R. Goswami, O. M. J. van `t Erve, B. T. Jonker

We inject spin-polarized electrons from an Fe/MgO tunnel barrier contact into
n-type Ge(001) substrates with electron densities 2e16 < n < 8e17 cm-3, and
electrically detect the resulting spin accumulation using three-terminal Hanle
measurements. We observe significant spin accumulation in the Ge up to room
temperature. We observe precessional dephasing of the spin accumulation (the
Hanle effect) in an applied magnetic field for both forward and reverse bias
(spin extraction and injection), and determine spin lifetimes and corresponding
diffusion lengths for temperatures of 225 K to 300 K. The room temperature spin
lifetime increases from {\tau}s = 50 ps to 123 ps with decreasing electron
concentration, as expected from electron spin resonance work on bulk Ge. The
measured spin resistance-area product is in good agreement with values
predicted by theory for samples with carrier densities below the
metal-insulator transition (MIT), but 100x larger for samples above the MIT.
These data demonstrate that the spin accumulation measured occurs in the Ge,
although dopant-derived interface or band states may enhance the measured spin
voltage above the MIT. We estimate the polarization in the Ge to be on the
order of 1%.

View original: http://arxiv.org/abs/1202.3994